Chromosomal banding patterns produced by methyl green-pyronin staining after trypsin treatment

A method is described for producing banding patterns with methyl green-pyronin (MGP) stain in chromosomes of fibrosarcoma cells. 1) The stain was made by mixing equal volumes of 2% aqueous pyronin G, 2% aqueous methyl green, distilled water, and 0.1 M acetate buffer (pH 5.7). 2) Treatment with colcemide and hypotonic KCl (0.075 M) was performed as usual. 3) Metaphase chromosomes were prepared using the flame-drying technique and treated with 0.25% trypsin at 37 C for 45 to 90 seconds. Before staining, the slides were rinsed in PBS, in distilled water, and then were dipped in 0.05 M acetate buffer. 4) Chromosomes were stained for more than 20 minutes, rinsed in distilled water, and hot-air dried. Satisfactory results were obtained in uncontracted metaphase chromosomes. MGP stain has the advantage of permitting much longer trypsin treatment and staining time than the trypsin-Giemsa method while providing satisfactory banding patterns.